Johst studied medicine and philosophy and - later - history of art. He joined the army in 1914. In 1918, he settled down at the Starnberger See.

His early work is influenced by expressionism (e.g., Der Anfang (1917), Der König (1920)). Later he turned to the naturalism psychology (Wechsler und Händler (1923), Thomas Paine (1927)).

In 1935, Johst became the President of the Reichsschrifttumskammer and of the Deutsche Akademie für Dichtung - organisations for German writers, but at this time just for writers who were producing pro-Nazi work. In the essay "Standpunkt und Fortschritt" (1933) he declared his agreement with Hitler's ideology.

Johst has gained notoriety for writing a line misattributed to Hermann Göring: